The biography uses mostly 'secondary' sources. [=information that did not come from original/primary sources but came from research done by others]
There are some 'secondary' issues/considerations which must be taken into account as well.
In some children's books, the text is 'secondary to' the illustrations.
(..) I say again: Hostile activity, mined area. Maintaining holding action. Carrying one wounded. Extracting to new location secondary P.Z. Over. Bravo Six, this is Avalanche. Negative on secondary rendezvous. Strongly suggest new location. Over. (..)1997 G.I. Jane